Light emitting device and method for manufacturing the same

ABSTRACT

Provided are a light emitting device and a method for manufacturing the same. The light emitting device comprises a first conductive type semiconductor layer, an active layer, a second conductive type semiconductor layer, and a light extraction layer. The active layer is formed on the first conductive type semiconductor layer. The second conductive type semiconductor layer is formed on the active layer. The light extraction layer is formed on the second conductive type semiconductor layer. The light extraction layer has a refractive index smaller than or equal to a refractive index of the second conductive type semiconductor layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 13/721,772 filed on Dec. 20, 2012, which claims priority to U.S.application Ser. No. 12/678,103 filed on Mar. 12, 2010, which claimspriority under 35 U.S.C. 119(a) to Korean Patent Application No.10-2008-0042973 filed on May 8, 2008 which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a light emitting device and a methodfor manufacturing the same.

BACKGROUND ART

Recently, studies are being actively conducted on a Light Emitting Diode(LED) as a light emitting device.

LED includes a first conductive type semiconductor layer, an activelayer, and a second conductive type semiconductor layer. Light isgenerated by combination of electrons and holes in the active layer whenpower is applied to the first conductive type semiconductor layer andthe second conductive type semiconductor layer.

LEDs are used for various machines and electrical and electronic devicessuch as display devices, lighting devices, mobile communicationterminals, and automobiles.

DISCLOSURE OF THE INVENTION Technical Problem

Embodiments provide a light emitting device and a method formanufacturing the same.

Embodiments provide a light emitting device and a method formanufacturing the same, which has improved light extraction efficiency.

Technical Solution

In one embodiment, a light emitting device comprises: a first conductivetype semiconductor layer; an active layer on the first conductive typesemiconductor layer; a second conductive type semiconductor layer on theactive layer; and a light extraction layer on the second conductive typesemiconductor layer, the light extraction layer having a refractiveindex smaller than or equal to a refractive index of the secondconductive type semiconductor layer.

In another embodiment, a method for manufacturing a light emittingdevice comprises: forming a first conductive type semiconductor layer,an active layer, and a second conductive type semiconductor layer;forming a selectively patterned mask layer on the second conductive typesemiconductor layer; forming a light extraction layer on the secondconductive type semiconductor layer on which the mask layer is notformed and removing the mask layer; performing a scribing process aroundthe light extraction layer; and selectively etching the secondconductive type semiconductor layer, the active layer, and the firstconductive type semiconductor layer to upwardly expose a portion of thefirst conductive type semiconductor layer.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features will be apparent fromthe description and drawings, and from the claims.

Advantageous Effects

The embodiments can provide a light emitting device and a method formanufacturing the light emitting device.

The embodiments can provide a light emitting device and a method formanufacturing the light emitting device, which has improved lightextraction efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a light emitting diode according to afirst embodiment.

FIG. 2 is a cross-sectional view taken along line I-I′ of the lightemitting diode according to the first embodiment.

FIG. 3 is a perspective view of a light emitting diode according to asecond embodiment.

FIG. 4 is a cross-sectional view taken along line II-II′ of the lightemitting diode according to the second embodiment.

FIGS. 5 through 10 are views illustrating a method for manufacturing alight emitting diode according to an embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings.

In the descriptions of embodiments, it will be understood that when alayer (or film), a region, a pattern, or a structure is referred to asbeing “on/under” a substrate, a layer (or film), a region, a pad, orpatterns, it can be directly on the substrate, the layer (or film), theregion, the pad, or the patterns, or intervening layers may also bepresent. Also, Further, the reference about ‘on’ and ‘under’ each layerwill be made on the basis of the drawings.

In the drawings, the dimension of each of elements may be exaggeratedfor clarity of illustration, and the dimension of each of the elementsmay be different from the actual dimension of each of the elements.

Hereinafter, a light emitting device and a method for manufacturing thesame will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view of a light emitting diode according to afirst embodiment. FIG. 2 is a cross-sectional view taken along line I-I′of the light emitting diode according to the first embodiment.

Referring to FIGS. 1 and 2, a light emitting diode according to a firstembodiment may include a substrate 10, a buffer layer 20, an undoped GaNlayer 30, a first conductive type semiconductor layer 40, an activelayer 50, and a second conductive type semiconductor layer 60.

A first electrode layer 80 may be formed on the first conductive typesemiconductor layer 40, and a second electrode layer 90 may be formed onthe second conductive type semiconductor layer 60.

Although not shown, a third conductive type impurity layer doped with afirst conductive type impurity may be formed on the second conductivetype semiconductor layer 60.

The light emitting diode according to the first embodiment may includean opening 110 to form the first electrode layer 80 therein. The opening110 may be formed by selectively removing the second conductive typesemiconductor layer 60, the active layer 50, and the first conductivetype semiconductor layer 40.

The upper side of the first conductive type semiconductor layer 40 maybe exposed by the opening 110, and then the first electrode layer 80 maybe formed on the first conductive type semiconductor layer 40.

Although not shown, the first electrode layer 80 and the secondelectrode layer 90 may be electrically connected to an external powersource. Also, an ohmic contact layer may be formed between the secondconductive type semiconductor layer 60 and the second electrode layer90. The ohmic contact layer may be formed with a transparent electrode.

A light extraction layer 70 may be formed on the second conductive typesemiconductor layer 60.

The light extraction layer 70 may be formed on a peripheral portion ofthe second conductive type semiconductor layer 60. Accordingly, thelight extraction layer 70 may be disposed to surround the exposedportion of the second conductive type semiconductor layer 60 and theopening 110.

The light extraction layer 70 may also be formed on all of theperipheral portions of the second conductive type semiconductor layer60.

The side surface of the light extraction layer 70 may be formed on thesame vertical plane as the side surface of the second conductive typesemiconductor layer 60.

The light extraction layer 70 may allow light from the active layer 50to be emitted to the outside more efficiently.

The light extraction layer 70 may be formed to have an inclined surface71 in an upwardly exposed direction of the second conductive typesemiconductor layer 60. The inclined surface 71 may be inclined at anangle of about 58 degrees to about 63 degrees with respect to the uppersurface of the second conductive type semiconductor layer 60.

The light extraction layer 70 may be formed to have a refractive indexsmaller than or equal to that of the second conductive typesemiconductor layer 60. For example, the second conductive typesemiconductor layer 60 may be formed of GaN, and may have a refractiveindex of about 2.33 with respect to light having a wavelength of about450 nm. The light extraction layer 70 may be formed ofAl_(x)Ga_(1-x)N_(y) (0≦x≦1), and may have a refractive index of about2.12 to about 2.33 with respect to light having a wavelength of 450 nm.The light extraction layer 70 may be formed of AlGaN.

As shown by the arrow in FIG. 1, since the light extraction layer 70having a refractive index smaller than or equal to that of the secondconductive type semiconductor layer 60 is formed on the secondconductive type semiconductor layer 60, there is an increasedpossibility that light generated in the active layer 50 may be reflectedby the upper surface of the second conductive type semiconductor layer60 to be emitted to the outside without being again incident to theinside. Particularly, the inclined surface 71 of the light extractionlayer 70 may allow the light to be emitted in the upward direction moresmoothly.

Although not shown, the ohmic contact layer may be formed between thesecond conductive type semiconductor layer 60 and the light extractionlayer 70.

FIG. 3 is a perspective view of a light emitting diode according to asecond embodiment. FIG. 4 is a cross-sectional view taken along lineII-II′ of the light emitting diode according to the second embodiment.

Referring to the FIGS. 3 and 4, the light emitting diode according tothe second embodiment may be similar to the light emitting diodedescribed in the first embodiment.

However, there is a difference in that the light emitting diodeaccording to the first embodiment is formed to have the opening 110exposing the first conductive type semiconductor layer 40 upwardly toform the first electrode layer 80, while the light emitting diodeaccording to the second embodiment is formed to have the opening 110 ofFIG. 1 to be opened in the direction of the side surface as well.

For this, portions of the second conductive type semiconductor layer 60,the active layer 50, the first conductive type semiconductor layer 40,and the light extraction layer 70 may be selectively removed.

The light emitting diode according to the second embodiment has anadvantage in that a process for electrically connecting the firstelectrode layer 80 to an external power source through a wire can bemore easily performed.

FIGS. 5 through 10 are views illustrating a method for manufacturing alight emitting diode according to an embodiment.

Referring to FIG. 5, a buffer layer 20, an undoped GaN layer 30, a firstconductive type semiconductor layer 40, an active layer 50, and a secondconductive type semiconductor layer 60 may be formed on a substrate 10.A mask layer 100 may be formed on the second conductive typesemiconductor layer 60 to form a light extraction layer 70.

For example, the substrate 10 may be formed of at least one of Al₂O₃,Si, SiC, GaAs, ZnO, and MgO.

The buffer layer 20 may reduce a difference in the lattice constantsbetween the substrate 10 and the nitride semiconductor layer stackedover the substrate, and may be formed in a stacked structure ofmaterials such as AlInN/GaN, In_(x)Ga_(1-x)N/GaN, andAl_(x)In_(y)Ga_(1-x-y)N/In_(x)Ga_(1-x)N/GaN.

The undoped GaN layer 30 may be formed by injecting a gas including NH₃and TMGa into a chamber.

The first conductive type semiconductor layer 40 may be a nitridesemiconductor layer doped with a first conductive type impurity. Forexample, the first conductive type impurity may be an n-type impurity.The first conductive type semiconductor layer 40 may be formed of a GaNlayer including Si as an n-type impurity.

The active layer 50 may be formed in a single quantum well structure ora multi-quantum well structure. For example, the active layer 50 may beformed in a stacked structure of InGaN well layer/GaN barrier layer.

The second conductive type semiconductor layer 60 may be a nitridesemiconductor layer doped with a second conductive type impurity. Forexample, the second conductive type impurity may be a p-type impurity.The second conductive type semiconductor layer 60 may be formed of a GaNlayer including Mg as a p-type impurity.

A third conductive type semiconductor layer (not shown) may be a nitridesemiconductor layer doped with a first conductive type impurity. Forexample, the first conductive type impurity may include an n-typeimpurity such as Si.

The mask layer 100 may be formed of a silicon oxide (SiO₂). The masklayer 100 may be patterned to form the light extraction layer 70according to an embodiment.

Referring to FIG. 6, the light extraction layer 70 may be formed on thesecond conductive type semiconductor layer 60 after the mask layer 100is formed.

The light extraction layer 70 may be formed of Al_(x)Ga_(1-x)N_(y)(0≦x≦1). For example, the Al_(x)Ga_(1-x)N_(y) may be formed by supplyingNH₃, TMGa and TMAl at a temperature of about 800° C. to about 1,000° C.For example, the light extraction layer 70 may be formed of AlGaN.

The light extraction layer 70 may be formed to have an inclined surface71 inclined at an angle of about 58 degrees to about 63 degrees withrespect to the upper surface of the second conductive type semiconductorlayer 60 during growth process.

The mask layer 100 may be removed as shown in FIG. 7.

Referring to FIG. 8, a scribing process may be performed around thelight extraction layer 70.

The scribing process is to divide a semiconductor layer into pieces tomake a plurality of light emitting devices. While a cross-sectional viewhas been illustrated in FIG. 8, the semiconductor layer may be dividedin a shape similar to a cube as shown in FIGS. 1 and 3.

Accordingly, the light extraction layer 70 may be disposed on theperipheral portion of the second conductive type semiconductor layer 60.The side surface of the light extraction layer 70 may be formed on thesame vertical plane as the side surface of the second conductive typesemiconductor layer 60.

Here, an ohmic contact layer (not shown) may be formed on the secondconductive type semiconductor layer 60, and then the mask layer 100 maybe formed on the ohmic contact layer. Thereafter, the light extractionlayer 70 may be formed over the ohmic contact layer.

Alternatively, after the light extraction layer 70 is formed on thesecond conductive type semiconductor layer 60, the ohmic contact layermay be formed on the second conductive type semiconductor layer 60 onwhich the light extraction layer 70 is not formed.

Referring to FIG. 9, a mask pattern (not shown) may be formed over thesecond conductive type semiconductor layer 60 and the light extractionlayer 70 described in FIG. 8, and then the second conductive typesemiconductor layer 60, the active layer 50, and the first conductivetype semiconductor layer 40 may be selectively etched to form theopening 110 as described in FIGS. 1 and 2.

Alternatively, the light extraction layer 70, the second conductive typesemiconductor layer 60, the active layer 50, and the first conductivetype semiconductor layer 40 may be selective etched along the maskpattern to form the opening as described in FIGS. 3 and 4.

Referring to FIG. 10, a first electrode layer 80 may be formed on thefirst conductive type semiconductor layer 40, and then a secondelectrode layer 90 may be formed on the second conductive typesemiconductor layer 60.

Accordingly, a light emitting diode can be manufactured as described inFIG. 1.

Thereafter, a process for electrically connecting the first and secondelectrode layers 80 and 90 to an external power source through a wiremay be performed, and a process for forming a molding member on thesecond conductive type semiconductor layer 60 and the light extractionlayer 70 may be performed.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

INDUSTRIAL APPLICABILITY

The embodiments can be applied to light emitting devices used as a lightsource.

The invention claimed is:
 1. A light emitting device comprising: asubstrate; a light emitting structure on the substrate comprising: afirst conductive type semiconductor layer; an active layer on the firstconductive type semiconductor layer; and a second conductive typesemiconductor layer on the active layer; a first electrode on the firstconductive type semiconductor layer; a second electrode on the secondconductive type semiconductor layer; and a light extraction structuredisposed above an edge area of the second conductive type semiconductorlayer, wherein the second electrode is disposed on a top surface of thesecond conductive type semiconductor layer, wherein the light extractionstructure is not disposed between the first electrode and the secondelectrode, wherein the light extraction structure includes a first wall,a second wall and a third wall, wherein at least two of the walls of thelight extraction structure have an inner surface inclined at an acuteangle, and wherein the second electrode comprises an electrode pad and atransparent electrode layer disposed between the electrode pad and thesecond conductive type semiconductor layer.
 2. The light emitting deviceaccording to claim 1, wherein the light extraction structure has arefractive index smaller than or equal to a refractive index of thesecond conductive type semiconductor layer.
 3. The light emitting deviceaccording to claim 1, wherein the light extraction structure comprisesAl_(x)Ga_(1-x)N (0≦x≦1).
 4. The light emitting device according to claim1, wherein the light extraction structure comprises AlGaN.
 5. The lightemitting device according to claim 1, wherein the first electrode isdisposed in an opening that is formed by selectively removing the secondconductive type semiconductor layer, the active layer and the firstconductive type semiconductor layer.
 6. The light emitting deviceaccording to claim 1, wherein the third surface is located around thesecond electrode.
 7. The light emitting device according to claim 1,wherein the light extraction structure is formed to surround the firstelectrode and the second electrode along the peripheral region of thesecond conductive type semiconductor layer.
 8. The light emitting deviceaccording to claim 1, wherein the light extraction structure and thesecond electrode are separated from each other on the second conductivetype semiconductor layer.
 9. The light emitting device according toclaim 1, wherein each inner surface is inclined at an angle of about 58degrees to about 63 degrees with respect to the upper surface of thesecond conductive type semiconductor layer.
 10. The light emittingdevice according to claim 5, wherein the first electrode and the firstconductive type semiconductor layer in the opening are upwardly exposed.11. The light emitting device according to claim 1, wherein the firstconductive type semiconductor layer which the first electrode isdisposed at is upwardly and laterally exposed.
 12. The light emittingdevice according to claim 1, further comprising an area that is removedfrom the light extraction structure to a part of the first conductivetype semiconductor layer.
 13. The light emitting device according toclaim 1, wherein the lateral side surfaces of the light extractionstructure, the second conductive type semiconductor layer, the activelayer, and the first conductive type semiconductor layer are arranged onthe same vertical plane.
 14. The light emitting device according toclaim 1, further comprising a buffer layer disposed between thesubstrate and the light emitting structure, wherein the secondconductive type semiconductor includes a p-type GaN layer and the firstconductive type layer includes an n-type GaN layer.
 15. The lightemitting device according to claim 1, further comprising a thirdconductive type semiconductor layer on the second conductive typesemiconductor layer, the third conductive type semiconductor layer beingdoped with an n-type impurity.
 16. The light emitting device accordingto claim 1, wherein an upper surface of the light extraction structureis even.
 17. The light emitting device according to claim 1, wherein afirst conductive type semiconductor layer is an N type semiconductorlayer and the second conductive type semiconductor layer is a P typesemiconductor layer.